[LeetCode OJ] Linked List Cycle 解题报告

#define INF 0x7fffffff
/**
* Definition for singly-linked list.
* struct ListNode {
*     int val;
*     ListNode *next;
*     ListNode(int x) : val(x), next(NULL) {}
* };
*/
class Solution {
public:
bool hasCycle(ListNode *head) {
return dfs(head);
}
bool dfs(ListNode *t){
if(t == NULL) return 0;
if(t->val == INF) return 1;
int tmp = t->val;
t->val=INF;
bool flag = dfs(t->next);
t->val = tmp;
return flag;
}
};